Fixing device for a shank chisel

ABSTRACT

A fixing device for a shank chisel, having a base part and an upper part, wherein the upper part is detachably connected to the base part. The upper part has an opening for receiving a shank chisel and the base part has a shaft opening, into which a shaft of the upper part is inserted, and the shaft has a tensioning surface that rests against the counter surface of a clamping element. The clamping element has a tensioning screw which is used to clamp the tensioning surface against the counter surface. The base part has a shoulder surface, which is located in the vicinity of or near the shank opening and at least partially surrounds the shank opening. A stop surface adjoins the rear region of the shoulder surface in the infeed direction at an angle. The upper part rests on the stop surface by a supporting surface and is held at a distance, at least in sections, from the base part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a holder for a shank chisel, which has a baseelement and an upper element, wherein the upper element can bereleasably connected with the base element, the upper element has areceptacle for a shank chisel, the base element has a shank receiverinto which the upper element is seated with the shank, and the shank hasa bracing face, against which a bracing element rests with acounterface. The bracing element has a bracing screw by which thebracing face can be braced on the counterface, the base element has anoffset face arranged near the shank receptacle and extends at leastpartially around the shank receptacle, wherein a detent face adjoins theoffset face at an angle near the latter which lies in the rear withrespect to the feed direction. The upper element is seated by a supportface on the detent face and is held, at least partially, spaced apartfrom the base element near the offset face.

2. Discussion of Related Art

A holder for a shank chisel is known from German Patent Reference DE 4322 401 A1. A base element is connected with a roller-shaped milling tubeof a milling machine, preferably a road milling machine. An upperelement is inserted with a shank into a shank receptacle of the baseelement.

The shank has a bracing face which is inclined relative to the insertiondirection. The base element has a screw receiver, which extends into theshank receptacle. A bracing screw can be rotated into the screwreceiver. On its end facing away from the screw head, the bracing screwhas a counterface that can be braced together with the bracing face ofthe shank, so that the upper element is securely held in the baseelement. If too strong of a tightening torque is exerted on the bracingscrew because of an operating error, the screw thread in the baseelement can sustain damage. Then, the base element has to be exchanged.During this, highly expensive down times of the machine are createdbecause the base element is welded to the milling tube. It must beburned out and a new base element must be welded into position. It isnecessary to keep the exact positioning of the new base element. Thebracing screw is embodied as a pressure screw. With its end facing awayfrom the screw head it rests on the bracing face of the shank and canundergo a mushroom-shaped flattening if there is too strong of atightening torque. The danger of damage to the screw thread because ofthis deformation arises when the bracing screw is turned out and thebase element would then be destroyed. The counterface of the bracingscrew which is braced on the bracing face of the shank is relativelysmall. A strong surface pressure then results if there are impermissiblystrong tightening torques. A bracing loss can occur as a result ofsettling of the material in the braced and threaded connection. Becauseof vibrations during the operation the danger then arises that the upperelement is released and the lower element is damaged.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a holder of the typementioned above but with a more user-friendly, sturdy fastening of theupper element on the base element.

This object is achieved with a bracing element that has at least onedisplaceable wedge, which has at least one screw receiver for thebracing screw, and the bracing screw is supported on the upper elementand is conducted through the support face and the detent face.

High bracing forces can be transmitted via the wedge of the bracingelement to the shank of the upper element. Even if damage to thethreaded connection exists, for example because of an operational error,it can be repaired without extensive down time of the machine. It isonly necessary to exchange the wedge having the screw receiver. The useof the wedge makes the employment of a tension screw possible. There isan advantage in that a release of the screw connection is prevented,even under large mechanical loads on the upper element, and inparticular in connection with vibrations. In this case the elasticity ofthe bracing screw allows compensation of settling without loss ofbracing. Because the bracing screw passes through the detent face of thebase element, a sturdy fastening results, along with a space-savingconstruction at the same time.

Optimally, in this arrangement the draw-in force transmitted to theupper element via the bracing screw is greater than the frictional forcecreated between the wedge and the shank. Then the upper element isalways held on the detent face of the base element, in a definitemanner.

In one embodiment of this invention, the bracing element and the upperelement are inserted into the wedge receiver and the shank receptaclefrom a top of the base element, and the bracing screw passes from thetop of the base element through a screw receiver of the upper element.This arrangement allows a simultaneous positive and non-positive bracingof the wedge element, and therefore of the upper element.

For making possible a dependable and time-saving mounting of thisarrangement, with the bracing screw the bracing element can be shiftedin the wedge receiver between a release position, which releases theshank of the upper element, and a bracing position which fixes the shankin place. In the released position a limit face of the bracing elementis in contact with a corresponding counterface of the wedge receiver,and the bracing screw is arranged so that its screw shank finds thescrew receiver in the release position.

For providing a sufficient bracing effect, but simultaneously also therelease of the wedge element without self-locking, an arrangement inaccordance with this invention is such that the wedge angle (α) of thebracing element is selected to lie in a range between 10° and 20°.

An especially compact construction can be achieved if the centerlongitudinal axis of the receptacle for the shank chisel intersects thecenter longitudinal axis of the bracing screw in the area of or near thescrew shank.

In order to build up only the least possible surface pressures in thebracing connection, in accordance with this invention the wedge of thebracing element is supported flat with respect to the shank of the upperelement and a wall of the bracing element receiver.

Thus the wall of the bracing element receiver and the bracing facetoward the shank should be embodied as large as possible.

A satisfactory snug fit of the upper element results in particular ifthe shank of the upper element is a pentagonal shank in cross sectionand has five flat shank faces, and the bracing element can be bracedwith a counterface flat against one of the shank faces.

In one embodiment, wear can be distinguished if the center longitudinalaxis of the bracing screw or a screw axis is arranged parallel with thelongitudinal axis of the shank of the upper element.

To simply increase the effective contact faces between the shank and thebracing element, the bracing face of the shank can be convexly orconcavely curved, and the counterface of the bracing element can becorrespondingly embodied as concave or convex.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is explained in greater detail in view of an exemplaryembodiment represented in the drawings, wherein:

FIG. 1 is a lateral view in vertical section of a holder with a baseelement and an upper element; and

FIG. 2 is a section as shown in FIG. 1, taken along line A-A through ashank area of the upper element as shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

A holder with a base element 20 and an upper element 30 is shown inFIG. 1. The base element 20 is placed with a lower seating face 21 onthe surface 11 of a tubular roller 10. The base element 20 can beconnected, for example welded together, with the tubular roller 10.Normally, a multitude of base elements are attached, lined up in ahelical shape, to the tubular roller 10. For this purpose, line-up faces28, 29 are on the base elements 20. The base element 20 has an offsetface 24 which, when viewed in a feed direction, makes a transition atits back to the detent face 25. The detent face 25 extends at an anglewith respect to the offset face 24. A shank receptacle 22 is cut intothe offset face 24. The shank receptacle 22 terminates in a clearancespace 23, which is set back with respect to the roller surface 11. Theshank receptacle 22 is widened by a wedge receiver 26 having a size of across section that widens, starting at the offset face 24, in thedirection toward the roller surface 11.

The upper element 30 can be fastened to the base element 20, which willbe later explained in greater detail. The upper element 30 has aprojecting shoulder 30.2, into which a bore as a chisel receiver 30.4 iscut, starting at a resting face 30.1. A round shank chisel, notrepresented in the drawings, can be inserted, rotatably seated, into thechisel receiver 30.4.

Here, the rotation of the round shank chisel occurs around the centeraxis 30.10. As FIG. 1 shows, the center axis 30.10 is placed at an acuteangle.

To make the mounting of the round shank chisel easier, the chiselreceiver 30.4 ends or terminates in an insertion widening in the area ofthe resting face 30.1. The chisel receiver 30.4 makes a transition intoa recess 30.5 at the end facing away from the resting face 30.1.

A receiver 30.6 for the head of a bracing screw 50 is drilled into theupper element 30 in the area of or near the recess 30.5. The receiver30.6 makes a transition into a screw receiver 30.7.

The upper element 30 has a support face 30.8 which is assigned to andrests against the detent face 25 of the base element 20. In theassembled state of the holder, the underside 30.9 of the upper element30 is at distance from the offset face 24.

Starting at the underside 30.9, a shank 30.11 projects away from theupper element 30. The shank 30.11 is inserted into the shank receptacle22 of the base element 20. Here, two front guide faces 30.12, which arearranged in a wedge shape with respect to each other, are supported on acorresponding centering device 22.1 of the base element 20, which isshown in greater detail in FIG. 2. On its rear and located opposite thebracing faces 30.12, the shank 30.11 has a flat guide face 30.13.

A bracing element 40 for holding the shank 30.11 in the shank receptacle22 is braced against the guide face 30.13.

The bracing element 40 is embodied as a displaceable wedge and isintroduced into the wedge receiver 26. The bracing element 40 can bemoved back and forth in the wedge receiver 26 between a bracing and arelease position by the bracing screw 50. The braced position is shownin FIG. 1. Here, the bracing element 40 rests with a counterface 40.1 onthe bracing face 30.13 of the shank 30.11. In the release position, thebracing element 40 can be shifted in the wedge receiver 26 until itrests with its limit face 40.2 on the bottom of the wedge receiver 26.The displacement movement of the bracing element 40 is guided on thewall of the wedge receiver 26 and thus forms a sliding face 40.3.

As mentioned above, the displacement of the bracing element 40 in thewedge receiver 26 is performed by the bracing screw 50. The bracingscrew 50 is introduced into the screw receiver 30.7. The screw head 50.1is protectively housed in the receiver 30.6. The screw shank 50.2 ispassed through the screw receiver 30.7 and is screwed with a threadedsection into a thread receiver 40.4 of the bracing element 40.

Starting at the released position, wherein the limit face 40.2 rests atthe bottom of the wedge receiver 26, the bracing element 40 can beshifted along the longitudinal axis 27 as a result of the turning of thebracing screw 50. The longitudinal axis 27 extends at the wedge angle αwith respect to the screw axis 50.3. The bracing element 40 can beshifted until it meets the bracing face 30.13 of the shank 30.11. Thenthe bracing element 40 presses the bracing faces 30.12 against theassociated centering device 22.1 of the base element 20. The bracingelement 40 is braced between the sliding face 40.3 and the bracing face30.13. In the braced state the shank 30.11 is clear of the rear borderof the shank receiver 22, so that a free space 20.2 results.

For disassembling the upper element 30 it is only necessary to releasethe bracing screw 50 and, if required such as due to self-locking,impeded by dirt or rust, etc., to bring it back with a light tap on thescrew head 50.1 into the release position. Then the upper element 30 canbe pulled out of the base element 20.

1. A holder for a shank chisel having a base element (20) and an upperelement (30), wherein the upper element (30) is releasably connectedwith the base element (20), the upper element (30) has a receiver (30.4)for a shank chisel, the base element (20) has a shank receptacle (22)into which the upper element (30) is seated with a shank (30.11) havinga bracing face (30.13) against which a bracing element (40) rests with acounterface (40.1), the bracing element (40) having a bracing screw (50)for bracing the bracing face (30.13) on the counterface (40.1), the baseelement (20) has an offset face (24) near the shank receptacle (22) andextending at least partially around the shank receptacle (22), a detentface (25) adjoins the offset face (24) at an angle which lies in a rearwith respect to a feed direction, and the upper element (30) is seatedby a support face (30.8) on the detent face (25) and is held, at leastpartially, spaced apart from the base element (20) near the offset face(24), the holder comprising: the bracing element (40) having at leastone displaceable wedge which has at least one screw receiver (40.4) forthe bracing screw (40), and the bracing screw (40) supported on theupper element (30) and conducted through the support face (30.8) and thedetent face (25).
 2. The holder in accordance with claim 1, wherein theclamping element (40) is inserted into a wedge receiver (26) whichadjoins the shank receptacle (22), that the shank (30.11) of the upperelement (30) limits a wedge receiver (26) in a first direction towardthe shank receptacle (22), and the wedge receiver (26) widens in asecond direction toward the free end of the shank (30.11).
 3. The holderin accordance with claim 2, wherein the bracing element (40) and theupper element (30) are inserted into the wedge receiver (26) and theshank receptacle (22) from a direction of a top of the base element(20), and the bracing screw (50) passes from the top of the base element(20) through a screw receiver (30.7) of the upper element (30).
 4. Theholder in accordance with claim 3, wherein with the bracing screw (50)the bracing element (40) is shiftable in the wedge receiver (26) betweena release position which releases the shank (30.11) of the upper element(30) and a bracing position which fixes the shank (30.11) in place, thatin the released position a limit face (40.2) of the bracing element (40)contacts a corresponding counterface of the wedge receiver, and that thebracing screw (60) is arranged so that a screw shank (50.2) of thebracing screw (60) finds the screw receiver (40.4) in the releaseposition.
 5. The holder in accordance with claim 4, wherein a wedgeangle (α) of the bracing element (40) is in a range between 10° and 20°.6. The holder in accordance with claim 5, wherein a first centerlongitudinal axis of the shank receptacle (22 intersects a second centerlongitudinal axis (60.3) of the bracing screw (50) near the screw shank(50.2).
 7. The holder in accordance with claim 6, wherein the wedge ofthe bracing element (40) is supported flat with respect to the shank(30.11) of the upper element (30) and a wall of the bracing elementreceiver (26).
 8. The holder in accordance with claim 7, wherein thatthe shank (30.11) of the upper element (30) has a pentagonal crosssection and has with five flat shank faces, and that the bracing element(40) is braced with a counterface (40.1) flat against one of the flatshank faces.
 9. The holder in accordance with claim 8, wherein a centerlongitudinal screw axis (50.3) of the bracing screw (50) is arrangedparallel to a longitudinal axis of the shank (30.11) of the upperelement (30).
 10. The holder in accordance with claim 9, wherein thecenter longitudinal screw axis (50.3) of the bracing screw (50) isarranged parallel to a longitudinal axis of the bracing element (40).11. The holder in accordance with claim 10, wherein the bracing face(30.13) of the shank (30.11) is one of convexly and concavely curved,and the counterface (40.1) of the bracing element (40) iscorrespondingly one of concave and convex.
 12. The holder in accordancewith claim 1, wherein the bracing element (40) and the upper element(30) are inserted into a wedge receiver (26) and the shank receptacle(22) from a direction of a top of the base element (20), and the bracingscrew (50) passes from the top of the base element (20) through a screwreceiver (30.7) of the upper element (30).
 13. The holder in accordancewith claim 12, wherein with the bracing screw (50) the bracing element(40) is shiftable in the wedge receiver (26) between a release positionwhich releases the shank (30.11) of the upper element (30) and a bracingposition which fixes the shank (30.11) in place, in the releasedposition a limit face (40.2) of the bracing element (40) contacts acorresponding counterface of the wedge receiver (26), and the bracingscrew (60) is arranged so that a screw shank (50.2) of the bracing screw(60) finds the screw receiver (40.4) in the release position.
 14. Theholder in accordance with claim 1, wherein a wedge angle (α) of thebracing element (40) is in a range between 10° and 20°.
 15. The holderin accordance with claim 1, wherein a first center longitudinal axis ofthe shank receptacle (22) intersects a second center longitudinal axis(60.3) of the bracing screw (50) near the screw shank (50.2).
 16. Theholder in accordance with claim 1, wherein the wedge of the bracingelement (40) is supported flat with respect to the shank (30.11) of theupper element (30) and a wall of the bracing element receiver (26). 17.The holder in accordance with claim 1, wherein the shank (30.11) of theupper element (30) has a pentagonal cross section with five flat shankfaces, and the bracing element (40) is braced with a counterface (40.1)flat against one of the flat shank faces.
 18. The holder in accordancewith claim 1, wherein a center longitudinal screw axis (50.3) of thebracing screw (50) is parallel to a longitudinal axis of the shank(30.11) of the upper element (30).
 19. The holder in accordance withclaim 1, wherein a center longitudinal screw axis (50.3) of the bracingscrew (50) is parallel to a longitudinal axis of the bracing element(40).
 20. The holder in accordance with claim 1, wherein the bracingface (30.13) of the shank (30.11) is one of convexly and concavelycurved, and the counterface (40.1) of the bracing element (40) iscorrespondingly one of concave and convex.